6256

RXRA

retinoid X receptor, alpha;RXRA;retinoid X receptor, alpha

nuclear receptor subfamily 2 group B member 1|retinoic acid receptor RXR-alpha|retinoid X nuclear receptor alpha

9q34.3

protein-coding

Vitamin D, in addition to its effects on bone, is important in cell cycle regulation. Vitamin D receptor (VDR) has been identified in breast, prostate, and colon cancers, as well as in canine and human osteosarcoma (OS) cell lines; however, it has not been well investigated in human OS-archived specimens. We correlated VDR, retinoid X receptor (RXR), and MIB-1 (Ki-67) expression in 110 archived OS cases with several clinicopathologic parameters including patient's age, sex, tumor location, tumor grade, and type and metastatic status. The expression of VDR and RXR was identified in human OS tissue obtained from primary and metastatic OS archival tissue. No statistically significant difference was found in VDR expression in relation with tumor grade, type, age, sex, or location. The expression of RXR was highest in higher-grade (P = .0006) and metastatic tumors but remained unchanged when correlated with tumor type, age, sex, or location. The expression of MIB-1 was statistically elevated in higher-grade tumors (P = .001), patients 25 years or younger (P = .04), tumors located in extremities (P = .005), and metastatic lesions, but was not impacted by tumor type or patient's sex. Proliferative activity was significantly reduced after treatment, as the mean MIB-1 expression dropped from 11% in primary biopsy samples to 6% in resection specimens. There appears to be a relationship between proliferative tumor activity and tumor grade, location, and metastasis. Additional studies on the analysis of the effects of vitamin D and RXR on OS proliferation, apoptosis, and differentiation are critical to further evaluate their potential role in OS treatment.

The expression of retinoid X receptor gamma (RXRgamma) and the clinicopathological parameters of total 69 patients with papillary thyroid carcinoma (PTC) larger than 1 cm were examined. The PTCs were classified into two groups according to the presence of loss of cellular polarity/cohesiveness (LOP/C). The expression of RXRgamma mRNA was examined by reverse transcriptase polymerase chain reaction and quantitative real-time PCR. The RXRgamma mRNA up-regulation was found to be positively correlated with extrathyroid invasion (r = 0.293, P = 0.019), advanced tumor stage (r = 0.318, P = 0.016) and lymph node metastasis (LNM) (r = 0.338, P = 0.005), as well as LOP/C (r = 0.345, P = 0.004), which was proposed as a histological characteristic of poor cellular differentiation. The RXRgamma mRNA expression, as well as extrathyroid invasion, LOP/C and advanced tumor stage, was further confirmed to be one of the independent predictive factors (Odds ratio: 6.545; 95% confidence interval: 1.575-27.208) of LNM using multivariate analysis. These results suggest that RXRgamma may play a role in the dedifferentiation and metastasis of PTC.